High-power, short-pulse laser irradiance can be used to optically write and store data in a solid dielectric substrate, such as glass. The irradiance induces at its focus a long-lived lattice perturbation caused by non-linear, multi-photon absorption by the substrate. In some cases, the lattice perturbation has the optical properties of a very small diffraction grating embedded within the substrate at the point where the irradiance is focused. Data written to a substrate in this manner can be read back using polarization imaging to interrogate the various grating-like perturbations formed within the substrate.